A team of US neuroscientists has identified "anxiety cells" in the brains of mice, an advance that may boost the treatment of humans suffering from anxiety disorders.

The researchers found the cells inside a structure called the hippocampus, a region of the brain vital for learning and memory. These cells were found to fire when the animal is anxious, triggering anxiety-related behaviours. But the cells probably exist in humans as well, said Rene Hen, Professor at Columbia University Irving Medical Center (CUIMC). "We call these anxiety cells because they only fire when the animals are in places that are innately frightening to them," Hen said. "For a mouse, that's an open area where they're more exposed to predators, or an elevated platform," Hen added.

The firing of the anxiety cells sends messages to other parts of the brain that turn on anxious behaviours, in mice, those include avoiding the dangerous area or fleeing to a safe zone. Though many other cells in the brain have been identified as playing a role in anxiety, the cells found in this study are the first known to represent the state of anxiety, regardless of the type of environment that provokes the emotion, the researchers said.

In the study, appearing in the journal Neuron, the team used a technique called optogenetics to control the activity of neurons using beams of light, the researchers found that the anxiety cells control anxiety behaviours. When the cells were silenced, the mice stopped producing fear-related behaviours, wandering onto elevated platforms and away from protective walls.

When the anxiety cells were stimulated, the mice exhibited more fear behaviours even when they were in "safe" surroundings. "This is exciting because it represents a direct, rapid pathway in the brain that lets animals respond to anxiety-provoking places without needing to go through higher-order brain regions," said Mazen Kheirbek, Assistant Professor at the University of California, San Francisco (UCSF). "Now that we have found these cells in the hippocampus, it opens up new areas for exploring treatment ideas that we didn't know existed before," said Jessica Jimenez, a doctoral student at CUMC.